Much ink has been spilled in recent weeks over Google's foray into the social media space. And while engineers at the search giant were busy setting Facebook squarely in their sites, the bean counters were ringing company cash registers to the tune of over $33 billion in revenue last year, thanks in no small part to advertising.

In fact, according to Google, 97 percent of company revenue comes from advertising, and a large portion of that from AdWords. For the uninitiated among us: AdWords is Google's main advertising product offering pay-per-click (PPC) advertising, cost-per-thousand (CPM) advertising, and site-targeted advertising for text, banner, and rich-media ads.

So obviously, Adwords is pretty important and with that in mind search marketing software and services firm Wordstream put together a list of the Top 20 Most Expensive Keywords in Google's Adwards Advertising platform.

If you are thinking of targeting any of these words make sure you've